// mods by James Zahary Dec 28, 2021 https://github.com/jameszah/ESPxWebFlMgr
// based on https://github.com/holgerlembke/ESPxWebFlMgr

//
// Copyright (c) 2013 Christopher Baker <https://christopherbaker.net>
//
// SPDX-License-Identifier:	MIT
//


#pragma once


#include "Arduino.h"


/// \brief A class for calculating the CRC32 checksum from arbitrary data.
/// \sa http://forum.arduino.cc/index.php?topic=91179.0
class CRC32
{
public:
    /// \brief Initialize an empty CRC32 checksum.
    CRC32();

    /// \brief Reset the checksum claculation.
    void reset();

    /// \brief Update the current checksum caclulation with the given data.
    /// \param data The data to add to the checksum.
    void update(const uint8_t& data);

    /// \brief Update the current checksum caclulation with the given data.
    /// \tparam Type The data type to read.
    /// \param data The data to add to the checksum.
    template <typename Type>
    void update(const Type& data)
    {
        update(&data, 1);
    }

    /// \brief Update the current checksum caclulation with the given data.
    /// \tparam Type The data type to read.
    /// \param data The array to add to the checksum.
    /// \param size Size of the array to add.
    template <typename Type>
    void update(const Type* data, size_t size)
    {
        size_t nBytes = size * sizeof(Type);
        const uint8_t* pData = (const uint8_t*)data;

        for (size_t i = 0; i < nBytes; i++)
        {
            update(pData[i]);
        }
    }

    /// \returns the caclulated checksum.
    uint32_t finalize() const;

    /// \brief Calculate the checksum of an arbitrary data array.
    /// \tparam Type The data type to read.
    /// \param data A pointer to the data to add to the checksum.
    /// \param size The size of the data to add to the checksum.
    /// \returns the calculated checksum.
    template <typename Type>
    static uint32_t calculate(const Type* data, size_t size)
    {
        CRC32 crc;
        crc.update(data, size);
        return crc.finalize();
    }

private:
    /// \brief The internal checksum state.
    uint32_t _state = ~0L;

};
